* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  user-select: none;
}
.content {
  height: 500px;
  background-color: red;
}
.button {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 6rem;
  height: 3rem;
  font-size: 1.5rem;
  background-color: white;
  border: none;
  border-radius: 5px;
  box-shadow: 1px 1px 5px black;
  transform: translate(-50%, -50%);
}
